Soluble silicate binder and method of making and using the same



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SOLUBLE SHJCATE BINDER AND METHOD OF MAKING bonded with sodium silicatelose much of their .strength upon being heated to red heat or above.

An object of the present invention is .to improve the binding propertiesof sodium and other 20 soluble silicates with a view to securing higherstrength in materials bonded therewith or a .reduction in the amount ofbinder required. A further object is to increase the refractoriness ofrefractory materials bonded with .sodium sili- 2 rate and to preserve athigh temperatures the strength of such refractories. I

A still further 'object of the invention is to provide a method whichmay be applied during .-the manufacture .of the silicate itself or .atthe 30 time of its use or incorporationwith thennaizrials .to be bonded.

'It will be apparent that sodium silicate, on "account of its low cost,is the water-soluble ailicate to be generally .used as a binder, butother soluble silicates come within the invention, although most of themare too expensive for commercial application. Potassium silicate isgenerally used for carbon arc pen sb'e'd'ause of 40 the differentcharacter of flame produced by the In accordance with the invention ahliphoshate is used in n with the soluble, silicate to constitute thebinder for he granular 45 or er materia 0 on ed together. The

alkali phosphate, if to be used dry, may be pulverizedand mixed with thematerialto be bonded, together with a dry soluble silicate yonly water"remaining to be added, or if preferred it may 501,6 dlssgl'm liquldsilicate before the latter is applie as a bond. The latter procedure isthe one to be followed wheh the combination of $01- uble silicate andalkali phosphate is to be .used as an adhesive, as for example inbonding sheet 55 material. In bondin g refractories and other Examiner2,077,258

annosmornasarm 0AM kvsf Norman Percy Pitt, Bockclifle, Ontario, and AlanFindlay Gill, Ottawa, Ontario, Canada 'No Drawing. Application June '26,1935, Serial No. 28,488 I 2mm. (01. ice-pf J This invention relates tosoluble silicate bindgranular materials equally good results are norersand to a method of making and using the mally obtained by the twomethods. same. It has been found that with this binder the Sodiumsilicate both in the wet and dry constrength of the :bonded material ismuch greater 5 dition, Has long been .used as a binder i'or various thanwhen the soluble silicate is alone, and i 5 types of materials. Forexample, as a binder further, that remmmrsafififim retain it has beenused inabrasives, refractory cements, a large proportion of "theirstrength after being asbestos cements and mortars or ac -prggf'heated,1being much superior in this respect to masonry an as anadhesivein asbestos paper, those bonded with sodium silicate alone. If demots,plywood, fibreboard, corrugated sired, advantage may be taken of thishigh 10 paper and laminated board.""lfn suitable applistrength to reducethe quantity of binder used, cations it produces a moderately strongbond, with a corresponding increase in refractoriness particularly afterdrying, and granular mateand reduction in cost. Reduction in the amountrials bonded with it usually have good tensile of sodium silicate usedin refractories usually restrength and modulus of rupture. Refractoriessuits in .a highly desirable increase in :the re- 15 .fractoriness ofthe bonded material.

While a1 0 bindr ublesilicatesht isnot necessar y particfil'ar*ratio'between theiiifthejratio offthe alkaliflfdfiihitddthmaterial tobe bonded being normally-the more'lirnportant. The proportio'nbf'alkali' acetate to refract ate or other ma erial to be bonded isusually in the neighborhood of but this proportion may-be varied greatlyin either direction within the scope of the invention. The exampleshereinafter given illustrate the ratio of alkali phosphate to solublesilicate, but it may be stated that, in general, an increase in thequantity of soluble silicate used does not require a correspondingincrease in the quantity of alkali phosphate required. In practice, thepercentage of alkali phosphate to be used in any given case must .bedecided, like that of the silicate itself, according to the strength,refractoriness and other properties desired in the bonded material, andthe economic factors involved. This is illustrated in the exampleshereinafter given and these also indicate the effect of difierent alkaliphosphates, the choice of which is largeiyidependent upon eco- .nomicfactors involved We sodium phos- 2 hate .is one .of the preferrecompounds, as t is re atively cheap, has desirable physical properties,.and ,gives excellent results. Qther alkali iphosphates which have beensuccessfully used .include the dibasic and monobasic SOdi ates mWWphosM-osp fie, sodium pyro'mp a an so um mospm If V prac ice e-invention'maybe appliedin a very wide field. In .fact, it appears that the ,additionof an alkali phosphate .will always improve a soluble silicate bondunless ltheohemical UNITED :STATES PATENT OFFICE.

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comparative results outlined above and as broadly I and 290 poundsindicated below.

1. Eject of additions of alkali hos hates to soluble silicate bonds forvarious T6;Tl10t01t88 Modulus of rupture after heating at- CompositionF. F. F.

Graded basic and neutral refractory with 4.5%

dry um silicate 350 240 265 Graded basic and neutral refractory with4.5% dry sodium silicate with 1% tripotassium phosphate..-. 975 625 430Graded basic and neutral liquid potassium silicate 80 8O Graded basicand neutral refractory w th 2.0% liquid potassium silicate with 1% iumphosphate 300 230 Graded basic refractory with 4.5% dry sodium silicate445 465 400 Graded basic refractory with 4.5% dry sodium silicate with1% trisodium phosphate 855 475 585 Special plastic refractory with 9.8%liquid sodium silicate 580 365 355 Special plastic refractory with 9.8%liquid sodium silicate with 1% trisodium'phosphate. 980 765 865 r 2.Eflect of additions of various 3129mm; and lzggglxgzjg acid to solublesi zcate bonds for refractories A Tensile strength after heating atComposition Special graded neutral refractory with 4.5% dry sodium p aGraded acid refractory with 14.1% liquid sodium silicate with 1%disodium phosphate. Bpecial graded acid refractory with 13.1% liquidsodium silics Special graded acid refractory with 13.1% li uid sodiumsilicate with 1% concentrated phosphoricacid 160 210 Specimens partiallyvitrified.

It will be observed that in every case, in spite of the wide variety ofconditions, there is a marked increase in strength where the phosphateis used.

3. A graded basic and neutral refractory with 4.5% dry sodium silicatewhen heated at 220 F. gave a. tensile strength of 135 pounds per squareinch. The incorporation in the mixture of 1% of sodium pyrophosphate,sodium glycerophosphate and sodium he'xametaphosphate respectivelyincreases the tensile strength to 200, 180 per square inch. A gradedacid refractory with 14% liquid sodium silicate gave a tensile strengthof 235 pounds per square inch when dried at 220 F. whereas the additionthere- Cross Reference .having when moistened and dried high unullllll lto of 1% trisodium phosphate increased the strength to 320.

4. A mixture of crushed firebrick and raw ground clay with 5% dry sodiumsilicate had a tensile strength after drying at 220 F. of pounds persquare inch. The mixture containing 1% trisodium phosphate had a tensilestrength of 185. Substituting burnt clay for the raw clay the respectivetensile strengths were 100 and 210 respectively, the addition of thephosphate more than doubling the strength of the bonded material. 'Ihisillustrates that in some cases the nature of the material to be bondedmay be such as, in effect, to eliminate the phosphate.

Tensile Material bonded Nature of bond strength Asbestos paper Sodiumsilicate 44 Do Sodium silicate plus 90 sodium phosphate Unsized paper Nobond 60 Do Sodium silicate 77 Do Sodium silicate plus 106 sodiumphosphate.

In the preferred practice of this invention 1% of trisodium phosphate(based on the weight of material to be bonded) is added with the desiredproportion of sodium silicate for the production of cements, refractoryor otherwise. When the combination of alkali phosphate and solublesilicate is to be used as an adhesive it is found that the use of onepart of trisodium phosphateto ten parts of sodium silicate (bothcalculated to the anhydrous condition) gives excellent results.

We claim:

1. As a new article of manufacture a water soluble binder consisting ofan alkali silicate and not more than an equal amount of alkaliphosphate.

2. .As a new article of manufacture, a. refractory material for furnacelinings and the like, having when moistened and dried high mechanicalstrength, consisting of particles of refractory material and uniformlymixed therewith a soluble silicate and an alkali phosphate.

3. As a new article of manufacture, a refractory material for furnacelinings and the like,

mechanical strength, consisting of particles of refractory material anduniformly mixed therewith a soluble silicate and an alkali phosphate tothe extent of not more than 10% by weight of the material to be bonded.

4. As a new article of manufacture, a refractory material for furnacelinings and the like, having when moistened and dried high mechanicalstrength, consisting of basic and neutral refractory materials, asoluble silicate binder and one-half to two percent by weight oftrisodium phosphate.

5. A method of manufacturing a refractory for use at high temperaturesin furnace linings and the like which consists in uniformlyincorporating in refractory material a soluble silicate and a solublephosphate.

6. A method of manufacturing a refractory for use at high temperaturesin furnace linings and the like which consists in uniformly incorand thelike which consists in uniformly incorporating in particles of basic andneutral reporating in refractory-material a. soluble silifractorymaterials a soluble silicate binder and cate and a soluble phosphate tothe extent of 0.5 to 2.0% of trisodium phosphate.

5 not more than 10% by weight.

7. A method of manufacturing a refractory for use at high temperaturesin furnace linings NORMAN PERCY PI'I'I'. ALAN FINDLAY GILL.

